Centralized traffic controlling system



Dec. 6, 1938. T. J. JUDGE I CENTRALIZED TRAFFIC CONTROLLING SYSTEM Filed Ma 25, 1952 v 6 Sheets-Shet 1 &0 3: 6 5.56 mzS T. J. JUDGE CENTRALIZED TRAFFIC CONTROLLING SYSTEM Filed May 25, 1952 6 Sheets-Sheet 3 %NVENTOR ATTORNEY Dec. 6, 1938.

Dec. 6, 1938. T. J. JUDGE I CENTRALIZED TRAFFIC CONTROLLING SYSTEM 6 Sheets-Sheet 4 Filed May 25, 1932 Dec. 6,1938. T. J. JUDGE 2,138,863

' CENTRALIZED TRAFFIC CONTROLLING SYSTEM Filed May 25, 1932 Sheets-Sheet 6 FIG.6. EGV fiav 4v IEav nzv EN nu Elm l (J i I I I I I 55 5 w L VP 6.) 4 i l Bfi .61,

i -45 FIG. 7. F|e..8.

Seleati ons Cede: CODE TABLE HIST I EZST Firs; 5 tep Second Step 281 1P3 IPF 2P3 ZPF 1 o g E .I' I vfl FIG. 9.

OPERATION CHART Operating Cycle Initiating Leak out Restoration Condition Period Period Transmitting Part ofCyc/e Period meat Fpnem SAQelag VP 1v VP 2v VP 5\/ VP 5A 25A Pick: up Picks up up up down up up up 'down down down Executing Periods V Conditioning Periods v Step5 P ste z ste .fl' fitep Storing Periods F P" l'" lndlcatmn I PL Transmlttmg Penods l i-- V INVENTOR v ATTORNEY ator in a central Patented Dec. 6, 1938 FATENT OFFIQE CENTRALIZED TRAFFIC CONTROLLING SYSTEM Thomas J. Judge, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application May 25, 1932, Serial No. 613,353

25 Claims.

This invention relates to centralized traffic controlling systems for governing trafiic on railroads, and more particularly pertains to the communication part of such systems. This invention is in the nature of an improvement over the prior applications of Hailes and De Long Ser. No. 526,674, filed March 31, 1931 and Preston Ser. No. 589,186, filed January 27, 1932, and no claim is made herein to any invention disclosed in either of said prior filed applications.

In a centralized traific control system of the type contemplated by this invention, the switches and signals at various points along a railroad system are placed under the control of an opercontrol ofiice, in such a way that the operator may at will change the position of the switches, subject to automatic approach and detector locking circuits which prevent unsafe operation of any switch, and in such a way that the operator may at will hold at stop any of the signals, or allow them to clear dependent upon the position of the associated switches and also provided the location of trains makes it safe for such signals to indicate proceed. Also, the system provides means whereby indications are displayed in the control office toinform the operator of the presence or absence of trains on the various track sections throughout the territory under his supervision, and to indicate the operated positions and conditions of the various switches; signals and the like.

The switches and signals are distributed throughout the territory, but the apparatus provided to govern those switches and signals which are located relative-1y near or adjacent to each other, is conveniently termed a field station. A communication system is then provided to interconnect the central control oflice with the several field stations for the transmission of controls to the field stations and for the reception of indications from the field stations.

In accordance with the present invention, the communication system is provided with three line wires toconnect the control office with each of the field stations, namely, a control line, an indication line, and a common return line. These three line wires serve to complete two line circuits, one for the transmission of controls, and the other for the transmission of indications.

As the system is of the coded duplex type, it is operable through cycles of operation for the transmission of controls and/or the transmission of indications. When controls are transmitted, a station selecting code is first transmitted to select the particular station with which communication is desired and then the controls are transmitted to that stationpand similarly, when indications are transmitted, the particular field station transmitting such indications first transmits a station registering code for registering which station is then transmitting, after which the indications are transmitted to the control office.

For the transmission of controls, a predetermined number of impulses of selected polarities are placed on the control line circuit for operating the apparatus at the control ofiice and at the field stations through cycles of operation irrespective of the character of the impulses, while the distinctive characters'of the impulses of such a series determines the particular station to be selected and the controls to be transmitted to the selected station.

For the transmission of indications, the presence or absence of impulses placed on the indication line circuit, during the steps of each cycle, as marked 01? by impulses placed upon the control line circuit, determines the particular station registered and the indications transmitted. During a cycle for the transmission of indications alone, only the apparatus at the field station transmitting and at the control office is operated, and the impulses placed on the control line circuit are of a non-selecting character; while, during a duplex cycle, the transmission of controls serves to mark off the steps for the impulsing of the indication line circuit.

One feature of the present invention resides in the manner in which the impulses are placed upon the indication line circuit, so as to double the capacity of such a circuit over that heretofore employed. For example, in systems of this type, one energizatio-n and one deenergization of the control line circuit has usually been designated as comprising a single step, with the field stations so arranged that indications are transmitted by pulsing the line circuit once for each step. However, in the system of the present invention, the indication line circuit is pulsed twice during each such step, namely, once during the energized 45 period of the control line circuit and once during the deenergized period of the control line circuit.

A system arranged in this manner increases the capacity for the transmission of indications to substantially double the capacity of the system for the transmission of controls. This is particularly desirable in a centralized trafiic control system, as it has been found in practice that the number of indications desired by the operator to supply proper information and the best facility 55 cal in train operation, is substantially double the number of controls necessary for positioning the trafiic governing devices under his supervision.

Another feature of the present invention resides in the manner in which the apparatus at the control ofiice and at all of the field stations operates step by step through cycles of operation for the transmission of controls alone or for the transmission of both controls and indications; while for the transmission of indications alone, only the apparatus at the control office and at the particular field station transmitting is required to operate. This functioning of the system is accomplished by allotting the first impulse of each cycle of operation to the determination of whether or not that cycle is to be for the transmission of controls. Such a feature is particularly desirable in order that the operations of the system may be limited to a minimum to eliminate wear on the various devices and to conserve in the use of power.

These characteristic features of the present invention thus briefly stated, will be explained more in detail in the following description of one embodiment of the invention and various other characteristic features, functions and advantages of a system embodying this invention will be in part pointed out and in part apparent as the description thereof progresses. I

In describing the invention in detail, reference will be made to the accompanying drawings, in which those parts having similar features and functions are designated throughout the several views by like letter reference characters which are generally made distinctive either by reason of distinctive exponents representative of their location or by reason of preceding numerals representative of the order of their operation, and in which:-

Fig. 1 illustrates the line circuit arrangement for a control ofi'ice of a system embodying the present invention together with the apparatus most closely associated with these circuits;

Fig. 2 illustrates the line circuits of two field stations in a system embodying the present invention together with the apparatus most closely associated with these circuits;

Fig. 3 illustrates the apparatus and circuit arrangements employed at a typical control office for providing means whereby an operator may govern the switches and signals throughout an extensive territory; and for providing means whereby indications may be received from the various field station locations throughout such territory;

Fig. e illustrates the apparatus and circuit arrangements employed at a typical field station for providing control of a single railroad track switch in accordance with the present invention, and for transmitting indications to the control ofiice;

Fig. 5 illustrates a modified line circuit arrangement of two field stations employed in a system embodying the present invention;

Fig. 6 illustrates in detail the circuits for the half step relay of the present invention;

Fig. '7 illustrates in detail the station selecting means shown in Fig. 4;

Fig. 8 illustrates a typical code table for the registration of field stations in the system of the present invention; and

Fig. 9 illustrates a chart of operation for the system of the present invention.

For the purpose of simplifying the illustration and facilitating in the explanation, various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have been em.- ployed, the drawings having been made more with the purpose of making it easy to understand the principles and mode of operation, than with the idea of illustrating the specific construction and arrangement of parts that would preferably be employed in practice. Thus, the various relays and their contacts are illustrated in a conventional manner, and symbols are used to indicate the connections to the terminals of batteries or other sources of electric current instead of showing all of the wiring connections to these terminals.

The symbols and are employed to in. dicate the positive and negative terminals respectively of suitable batteries or other sources of electrical energy; and the circuits with which these symbols are used always have current flowing in the same direction. The symbols (B+) and (B) are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of current having mid taps designated (CN) and the circuits with which these symbols are used may have current flowing in one direction or the other depending upon whether the terminal (B+) or (B-) is used in combination with the center tap (CN). When alternating current is used in place of direct current, the particular symbols employed represent relative instantaneouspolarities.

Communication system generaZZy.-The general plan of organization of the system may be best understood by placing Figs. 1 and 2 end to end illustrating the line circuits of a system having a control omce and two field stations. It is to be understood of course that the system may be extended to have as many field stations as desired, but for convenience in disclosing the present invention, only a first and a second field station have been illustrated. A control line wire l0 connects the control ofiice to the first field station, connects the first field station with the second field station, and so on, to the end of the system where it is then connected to the common return line i2 which extends from the control ofiice through each of the field stations. The control line includes a three position biased-to-neutral polarized line relay F (with suitable exponent) at the control oifice and at each field station. In the control oflice, the control line circuit passes through contacts of an impulsing relay E and an impulse repeating relay EP which open and close the circuit to mark off the impulses of each cycleof operation, while pole changing contacts of a polarity determining relay D determine the character of each of the impulses supplied'from a control battery CB.

An indication line it extends from the control omce to the first field station, from the first field station to the second field station, and so on through each of the field stations, but this line is open ended at the last field station, that is, it is not connected to the common return line. At each field station, the indication line l4 includes a back contact of a change storing relay CHS (with suitable exponent) which opens, when picked up, the indication line extending to the succeeding field stations and connects the sending apparatus at the corresponding field station between the indication line I4 and the common return line l2.

At the control office, the indication line includes either a message receiving relay MEB or a message receiving relay MEF depending upon whether the control line is energized or de-energized, as repeated by an impulse repeating relay ZFP. The letter B of the reference character MEB indicates that this relay is included when a back contact of the relay 2F? is closed; while the letter F of the reference character MEF indicates that this relay is included when a front contact of the relay ZFP is closed. Energy for the indication line' circuitis supplied by an indication battery 13 having one terminal connected to the common return line l2.

Control ofiice equipment-The control oflice (see Fig. 3) includes a control machine having a group of control levers for each of the field stations, a miniature track lay-out corresponding in every way to the actual track lay-out in the field, and various indicating lamps or equivalent devices together with apparatus and circuits to accomplish the desired functioning of the system.

That part of the control ofiice illustrated, shows more particularly that part of a control machine which is typical of the apparatus associated with a single field station having a track switch, a cross-over or the like, together with the general transmitting apparatus employed for all such field station units of apparatus.

This apparatus for one track switch comprises a switch machine control lever SML, a self-restoring starting button SB, a miniature track switch ts, and a track occupancy indicating lamp OS. Similarly, a signal control lever or levers (not shown) would also be associated therewith but for convenience has been omitted, as the control of a track switch may be considered as typical of the control of other types of traflic controlling devices.

The movement of the switch machine control lever SML from one extreme position to the other followed by the actuation of the starting button SB results in the normal or reverse operation of the corresponding track switch at the corresponding field station controlled through the medium of the communication system of the present invention. The momentary actuation of the starting button SE is preferably stored by a suitable storing relay (not shown) which in turn picks up the corresponding code determining relay CD for the associated station. Such control has been merely indicated in order to simplify the present disclosure.

The storing relays for each starting button and their corresponding code determining relays are so interlocked that irrespective of the numher of storing relays that are energized simultaneously or in rapid succession, only onecode determining relay for a particular station may be energized or picked up during any one particular cycle of operation. This interlocked bank of relays is so arranged that if several storing relays are energized at the same time, their corresponding code determining relays CD will be energized successively during successive operating cycles in a predetermined sequence or order determined by their relative location in the code determining bank of relays, all of which has been completely disclosed in the application of N. D. Preston et al., Ser. No. 455,304, filed May 24, 1930, corresponding to Australian Patent 1501 of 1931.

The control ofiice includes, as previously mentioned, a control line relay F of the three posi tion biased-to-neutral polarized type. This line relay F has a neutral quick acting repeating relay FP, which repeats each energization and each deenergization of the line relay F, irrespective of the polarity with which the relay F is energized. For

purposes hereinafter pointed out, the quick acting neutral relay FF is provided with a repeating relay ZFP, also of the quick acting neutral type.

A slow acting line repeating relay SA is picked up at the beginning of each cycle of operation and is dropped at the end of each cycle of operation. This slow acting relay SA has such characteristics that its pick-up time is relatively slow compared to the pick-up time of the neutral relays FF and EFP, for example, but is relatively quick in picking up as. compared with its dr'op away period. The drop away period of this relay SA is sufficiently retarded, that its contacts remain in picked up positions between successive impulses applied to the control line circuit during a cycle of operation, as repeated by the neutral relay ZFP. Also, the relay SA has a repeating relay ZSA associated therewith for purposes hereinafter pointed out.

Associated with the line relay F and its repeating relays, a bank of stepping relays, including relays lV, 2V and 3V, together with a half step repeating relay VP, are provided to mark off the successive steps of each cycle of operation.

An impulsing relay E is jointly controlled by the stepping relays and the half step relay VP and this impulsing relay together with its repeating relay EP govern the opening and. closing of the control line circuit.

The polarity of the impulses applied to the control line circuit from the control battery CE, is determined by a three position biased toneutral polarized relay D which is controlled on each step of an operating cycle in accordance with the station code and the controls to be transmitted for that particular cycle of operation.

As previously mentioned, the two neutral message receiving relays MEB and MEF are provided to repeat the conditions of the indication linev circuit during the deenergized and energized con ditions of the control line circuit respectively. The conditions of these relays during such periods of time for each step are stored in suitable pilot relays and indication storing relays for registering the station having indications to transmit and for registering the indications transmitted.

For the purpose of illustrating station registration, the pilot relays l PB and IPF are used for the first step, and similar pilot relays ZPB and ZPF (not shown) may be provided for the second step, and so on until a. sufficient number of codes for station registration have been provided. These pilot relays are of the two position polarized magnetic stick type, although it is to be understood that any suitable type arrangement of pilot relays maybe employed. The indication receiving relays such as relay IR, for example, are also of the two position polarized magnetic stick type for storing the indications transmitted from the field.

A relay C is provided as a starting and control office cycle controlling relay. In other words, whenever the system is initiated from the control office for transmitting controls, this relay C is picked up at the beginning of the cycle and is maintained picked up until the end of the cycle.

Similarly, a relay F0 is provided as a field starting and cycle controlling relay which is picked up whenever the system is initiated into a cycle of operationfrom the field and is maintained picked up until the end of such operating cycle.

The control office also includes various sources of current supply, bus Wires and circuit connections, indicator lamps, terminal boards, overload protection, and such other devices as may be required for the proper functioning of such a system.

Field station equipment-The field station illustrated in Fig. 4 is typical of all field stations of the system and may be adapted to be used at the first, second or any other location by merely altering certain code jumpers and selections to arrange for the desired codes, but for convenience in the description, it has been specifically illustrated as the first field station by reason of the distinctive exponents employed.

With reference to Fig. 4, a turn-out track is illustrated as connected to a main track by means of a track switch TS. This track switch is operated from one extreme locked position to the other by a suitable switch machine SM.

This switch machine SM is operated by a switch machine control relay SMR which is of the two position polar magnetic stick type, and which is governed from the control oifice through the medium of the communication system herein disclosed. The relay SMR controls the operation of the switch machine SM by energizing its normal or reverse operating wires from a source local to the field station in any suitable well known manner, which control preferably includes suitable approach locking means and such other automatic signalling means as is usually employed, but which is not shown in the present disclosure for the purpose of simplifying the description of the present invention.

The switch machine SM, although only its remote control has been illustrated, may employ a dual control selector in the usual manner without in any way adding or detracting from the application of the present invention.

Suitable signals are associated with the track switch TS for governing traffic thereover and are provided with automatic signalling means interrelating the traffic over this track switch with such other sections of track and trafiic controlling devices as may be associated therewith. These signals are also contemplated as being governable from the control ofiice through the medium of k the communication system in any suitable way by control relays operated from the control office similarly as the switch machine control relay SMR all of which has been omitted for the sake of simplifying the present disclosure.

A detector track section having a normally closed track circuit with the usual track relay T and a suitable track battery is also associated with the track switch TS for indicating the passage of trains thereover.

The communication part of the system includes at the field station a three position biased-to-neutral polar line relay F as previously mentioned, together with its quick acting line repeating relay FP These relays and relay SA have similar characteristics as the corresponding relays in the control office, the only difference being that the relay SA is controlled directly by the relay Fl? instead of by a repeater of the relay PP.

The field station includes a bank of stepping relays IV 2V and 3V together with a half step relay VP arranged in a similar manner as the stepping relay bank in the control office.

Associated with the stepping relay bank is a checking relay K which registers at the beginning of each cycle of operation whether or not that cycle is to be for the transmission of controls to a selected field station. If the cycle of operation is for the transmission of controls, then the polar contact of this two position polarized magnetic stick type relay is positioned so as to allow the operation of its associated stepping. relay bank; while if the cycle of operation is for the transmission of indications only, then the polar contact of this relay is operated to the opposite position and its associated stepping relay bank remains at rest, unless the station at which it is located is the one which is to transmit indications.

For the purpose of illustrating the selection of a station, the station selecting relays IST and 2ST of the two position polar magnetic stick type have been illustrated, but it is to be understood that any suitable station selecting apparatus may be employed and still practice the present invention.

A change relay CH is provided to register a change in any of the traflic controlling devices at the station, so that the system will be initiated for the transmission of the new indications. Although this change relay has been shown as responsive only to a change in the position of the track relay T, it is to be understood that its holding stick circuit may be carried through any number of devices, so as to register a change in a large number of similar devices.

A change storing relay CHS together with a lock-out relay LO are employed at the fleld station in connection with the indication circuit to determine when this field station is to transmit its new indications. Whenever the lockout relay L0 and the change storing relay CHS are properly positioned during a cycle of operation to permit the field station to transmit, a pulsing relay PL is governed in accordance with the code jumpers and the indication contacts for this station, so that impulses are placed upon the indication line circuit to register the station in the control ofiice and to transmit the various indications.

A resistance R is employed to compensate for the distance between the field station and the control ofiice. In other words, the field station at the end of the line needs no resistance R (with suitable exponent), but for each station nearer the control oflice, a higher resistance is required, so that the same current from the indication battery IB in the control oifice always flows during an indication cycle irrespective of what particular station is transmitting.

The field station also includes suitable bus wires, circuit connections, code jumpers, overload devices, and other devices necessary for a centralized traffic control system as contemplated in accordance with the present invention.

It is believed that the nature of the invention, its advantages and characteristic features can be best understood with further description being set forth from the standpoint of operation.

Operation The system of the present invention is normally in a condition of rest, but may be initiated into a cycle of operation either from the control ofiice or from any of the field stations whenever there are new controls or new indications ready to be transmitted. If new controls for several different field stations are ready for transmission at substantially the same time, the controls for the several stations are transmitted on separate cycles of operation, one station for each such cycle. Similarly, if several field stations have indications ready for transmission at the same time, the indications are transmitted from such field stations to the control oflice, one station at a time on separate operating cycles.

speed.

It may happen, that there are new controls and new indications ready to be transmitted at the same time, and in such instances controls are transmitted to a selected field station and simultaneously therewith indications are transmitted from that field station or some other field station during the same cycle of operation.

Irrespective of whether a cycle of operation is to be for the transmission of controls and/or .the transmission of indications, a predetermined number of impulses are placed upon the control line circuit to accomplish the step-by-step operation of the stepping relay banks. These impulses placed upon the control line circuit are time spaced, that is, the impulses follow each other at definite time intervals. That period of time during which the control line circuit is energized with an impulse is conveniently termed an executing period, while the deenergized period of V the control line circuit between successive impulses is conveniently termed a conditioning period. Also, for convenience in describing the present invention, the normal condition of the -system between successive cycles of operation is conveniently termed a period of blank or a condition of rest.

When a cycle of operation is initiated for the transmission of controls, the character of the plurality of impulses placed upon the control line circuit is determined in accordance with the station to be selected and the controls to be transmitted as set up by the code jumpers and control levers for that station. On the other hand, during a cycle of operation initiated for the transmission of indications alone, the character of the plurality of impulses placed upon the control line circuit is such as to fail to select any station, but merely to cause the step-by-step operation of the control office stepping relay bank and the particular field station having indications to transmit.

When a cycle of operation is initiated from a field station for the transmission of indications, during the plurality of impulses placed upon the control. line circuit to cause the step-by-step operation, the indication line circuit is pulsed, that is, it is either energized or deenergized during both the executing period of the step and on the conditioning period of the step. In other words, the indication line circuit receives impulses for each half of each step, thereby doubling the capacity of the indication line circuit as compared to the control line circuit.

Although the condition of the indication line circuit may be changed twice during each step, this operation is no faster than the operation of the control line circuit, as the condition of the control line circuit is also changed twice for each step. In other words, the control line is energized and de-energized to comprise a step, and the maximum changes that may occur in the indication line circuit is a similar condition of energization and de-energization, or vice versa. Thus, the system of the present invention provides a line circuit arrangement in which both the control line and the indication line are operated at the same Normal at rest conditz'0ns.Although the system may be initiated from the field stations, the line circuits are normally dc-energized, and similarlythe remaining circuits of the system are arranged to be normally de-energized with a few exceptions.

For example, the track circuit associated with the track switch TS (see Fig. 4) is preferably of the closed circuit type. Also, the change relay CH is normally energized by a stick circuit closed from through a circuit including front contact 15 of the track relay T, front contact l6 of relay CH winding of relay CH to Manual starting.-With the system in a condition of rest or a period of blank, it may be manually initiated into a cycle of operation for the transmission of controls. Whenever such a cycle of operation is desired, the operator first positions the control levers for the field station which he desires to control then actuates the starting button associated with that station.

Whenever the starting button for a station is actuated, such actuation is suitably stored or registered and if the system is in a condition of rest or a period of blank, the code determining relay for that station is immediately energized. However, the code determining relays for the several stations are so interlocked that if several starting buttons are actuated successively or simultaneously, only one code determining relay may be picked up at any one time. Thus, the code determining relays are energized successively for successive cycles of operation. Such interlocking for the several stations has not been disclosed in detail but is understood to be of any suitable type.

For the purpose of considering the operation of the present system, it is sufficient to know that the actuation of the starting button SB (see Fig. 3) causes the actuation of the corresponding code determining relay CD which cannot be up when any one of the other code determining relays (not shown) is picked up. Also, the actuation of the starting button SB completes a pick up circuit for the cycle controlling and starting relay C from including back contacts ll and 58 of relays FF and 2SA respectively, upper winding of relay C, the back point of the starting button SB, to

Such energization of the starting relay C, completes a stick circuit, as soon as its contacts assurne picked up positions, from including back contact IQ of relay ZSA, front contact 20 of relay C, lower winding of relay 0, to This stick circuit for the relay C including back contact E9 of relay ZSA is opened during the cycle of operation, but pri or to its opening positive energy from (-1-) is applied to the circuit through front contact 25 of relay SA. In other words, during the period of blank the stick circuit is closed through back contact IQ of relay 2SA, then at the beginning of a cycle of operation the relays SA and ESA are picked up successively, thereby closing front contact 2| before opening back contact I9.

. At the end of a cycle, later to be pointed out, the relays SA and 2SA are de-energized successively, thereby opening front contact 2! before closing back contact l9 so that the relay C can drop away during the retarded release of the relay ZSA.

The picking up of the contacts of the relay C conditions the polarity determining relay D for the application of impulses of selected polarity on each step, as presently to be described.

Polarity selection of stepping impulses.-When ever the system is initiated from the control office resulting in the energization of the starting relay C (see Fig. 3), the first impulse placed upon the control line circuit is positive in character by reason of a circuit from (B|-) including back contacts 22, 23 and 24 of stepping relays 6V, 2V and 3V respectively, front contact 25 of relay C,

windings of relay D, to (ON). This energization of the relay D actuates its polar contacts to right hand positions for placing a positive impulse upon the control line circuit.

More specifically, the control line circuit is energized from the positive terminal of the control battery CB (see Figs. land 2), including polar contact 23 of relay D in a right hand position, back contacts 2'5 and 28 of relays E and EP respectively in multiple, windings of line relay F at the control ofiice, control line wire II) to the first field station, windings of the line relay F at the first field station, control line wire In to the second field station, windings of the control line relay F at the second field station, to the common return line wire I2 and thence through the several stations to the control office, polar contact 29 of relay D in a right hand position, to the negative terminal of the control battery CB.

This application of energy to the control line circuit of course causes various relay operations, a description of which for the time being will be omitted, it being assumed that after a predetermined time the control line circuit is opened by the impulsing relays E and EP. Such de-energization of the control line results in the energization of the first stepping relay IV. The picking up of the relay IV opens back contact 22 and connects the relay D to the code bus 30 through front contact 22. In this case, the code buses 33, 3I and 32 are energized in accordance with the positions of the code jumpers 33 and 34, and control lever SML respectively, as the relay CD is energized.

With the code jumper 33 in an upper position, positive potential from (B+) is applied to the code bus 30 through front contact 35 of relay CD, and hence the contacts of the relay D are maintained actuated to right hand positions. On the other hand, if the code jumper 33 were in a lower position, negative potential from (B) would be applied to the code bus 30 through front contact 35 of relay CD, and the contacts of the relay D would be actuated to left hand positions.

Such control of the relay D upon the picking up of the relay IV occurs during the first conditioning period, that is, during the de-energized condition of the control line circuit following the first impulse. Thus, upon the closure of the back contact 21 of the relay E, the control line is energized with a particular polarity in accordance with the position of the code jumper 33 as repeated by contacts of the relay D.

After the second impulse has been upon the control line circuit for a predetermined period of time, the circuit is again opened by the picking up of contacts 21 and 28 of the relays E and EP respectively. Such de-energization of the control line causes the second step to be taken by ener-. gizing the stepping relay 2V. The relay D is connected through front contact 23 of the relay 2V to the code bus 3I which is energized in accordance with the position of the code jumper 34 in a similar manner as explained in connection with the code bus 33 for the first step.

If the code jumper 34 is in an upper position, negative potential from (B) is applied to the code bus 3I through front contact 36 of relay CD actuating the contacts of the relay D to left hand positions, while if the code jumper 34 is in a lower position, the code bus 3| is energized with positive potential from (B+) and the contacts of the relay D are actuated to right hand positions. In either case, the relay D changes positions, while the control line circuit is open, thereby assuming proper positions in readiness for the next c sure of thecircuit by the impiiisi'ng relays EandEP.

This operation occurs on each step so that the rel'ayD is energized in accordance with the polarity applied to' the respective code buses for each step. During the first part of each such operating cycle, the code buses for the corresponding steps are energized with positive or negative potentials in accordance with the character of the code for the station desired to be selected; while on the remairiin'gsteps of the cycle, the code buses are energized in accordance with the positions of the control levers for the selected station.

For example, the code bus'32 for the third step is energized in accordance with the position of the control lever SML, so that positive or negative potential from (13+) or (B) is applied to the code bus 32 through front contact 31 of the relay CD depending'upon whether the control lever SML is in right or left hand positions re.- spectively. Thus, the contacts of the relay D are actuated to right or left hand positions during the conditioning period following the third 1m.- pulse for determining'the positive or negative character of the fourth impulse placed upon the control line circuit.

From the above, it will be seen that the impulses on the control line circuit always begin with apositive impulse for a cycle of operation initiated from the control office, while the following impulses are of positive or negative character dependent upon the codejumpers and control levers rendered effective by theparticuiar code determining relay energized for that cycle. F

Also, this polarity determination-is accomplished by a polarity determining relay'D having the polarity of its energization dependent upon. the positions of the respective devices. for the several steps-,with the changes in selection occurring while the control circuit is de-energized.

Operation o'fstepping' relay bank-The manher in which the control line circuit is initially energized at the beginning of'a cycle of operation for the transmission of controls has been pointed out above. In accordance with the particular polarity of this first impulse, the contacts of the line relays F are operated to right or left hand positions. However, irrespective of. the partic- F are energized, their repeating relays FP are energized by circuits obvious from the drawings. For example the actuation of polar contact 3 8 of relay F to either of its positions (see Fig. 3) connects positive energy to one terminal of the relay FP, while negative energy is permanently connected to its opposite terminal.

The closure of front contact 39 of the relay FP in the control office completes a circuit for its repeating relay 25?, as. obvious from the drawings. The picking up of the contacts of the relay 2F? energizes the relay SA through front contact 40, and after a time the contacts of the relay SA are picked up. The closure of the front contact 4I of relay SA completes a pick-up circuit for the relay 28A, and after a time its contacts pick up.

In brief, the relays F, FP, ZFP, SA and ZSA pick up in succession, each being a direct repeater of the next preceding relay. These successive relay operations mark off the various stages in the initiation of the system at the beginning of each cycle. For example, the picking. up of the contacts of the relays FP (with suitable exponents) at the control office. and at each field station marks the end of the initiation period and the 'ular polarity with which the control. line. relays beginning of the look-out period; while the picking up of the contacts of the relays SA (with suitable exponents) at the control oflice and at each field station marks the end of the look-out period and the beginning of the transmitting part of the cycle.

Forgetting for the time the various operations which occur during the starting of the system, and assuming that a predetermined time after the picking up of the relays SA the control line is de-energized followed by energizations and deenergizations alternately, we may consider the operation of the stepping relay banks.

At the beginning of the transmitting part of the cycle marked off by the picking up of the contacts of the relays SA at the control oflice and at each field station, the half step relays VP are picked up preparing their respective stepping banks for the first step, which is taken on the next de-energization of the line circuit. In brief, the half step relays VP are picked up and dropped alternately by the successive energizations of the control line circuit; while the stepping relay banks each take one step for each successive de-energization of the control line circuit.

Although the stepping relay banks at the control office and at each field station are similar, the description will be directed more particularly to the control oiiice (see Fig. 3) and to the simplified layout of the half step relay circuits (see Fig. 6).

More specifically, the picking up of the contacts of the relay SA with the relay ZFP already picked up, immediately closes a pick-up circuit for the relay VP. This pick-up circuit is closed from through a circuit including front contact 42 of relay SA, front contact 43 of relay ZFP, back contact 44 of relay IV, windings of relay VP,

to As soon as the contacts of the relay VP have picked up, a stick circuit is closed from through a circuit including front contact 42 of relay SA, front contact 45 of relay VP, back contact 44 of relay IV, windings of relay VP, to

Upon the following de-energization of the control line circuit (first), the relay ZFP is de-energized thereby closing a. pick-up circuit for the relay IV from through a circuit including front contact 46 of relay SA, back contact 41 of relay ZFP, front contact 48 of relay VP, back contact 49 of relay 2V, windings of relay IV, to As soon as the contacts of the relay IV are picked up, a stick circuit is closed from through a circuit including front contact 45 of relay SA, front contact 50 of relay IV, windings of relay IV, to Although the stick circuit for relay VP, including back contact 44, is opened when relay IV is picked up, the relay VP is energized through another stick circuit closed by relay ZFP prior to the picking up of relay IV.

Upon the following energization of the line circuit (second), as repeated by the relay ZFP, the relay VP is deenergized as its stick circuit including front contact is opened at back contact 43 of relay ZFP, and as its stick circuit including front contact 45 is opened at back contact 44 of relay IV.

The next deenergized condition of the control line circuit (second), as repeated by the relay 25?, causes the second stepping relay 2V to be energized from through a circuit including front contact 46 of relay SA, back contact 41 of relay 2FP, back contact 48 of relay VP, back contact 52 of relay 3V, front contact 53 of relay IV, windings of relay 2V, to As soon as the contacts of relay 2V are picked up, a stick circuit is closed from through a circuit including front contact 46 of relay SA, front contact 54 of relay 2V, windings of relay 2V, to

The following energized condition of the line circuit (third), as repeated by the relay ZFP, closes the pick-up circuit for the relay VP from through a circuit including front contact 52 of relay SA, front contact 43 of relay 2FP, back contact 55 of relay 3V, front contact 56 of relay 2V, windings of relay VP, to The closure of front contact 45 of relay VP completes a stick circuit for relay VP from through a circuit including front contact 42 of relay SA, front contact 45 of relay VP, back contact 55 of relay 3V, front contact 55 of relay 2V, windings of relay VP, to

The next deenergized condition of the control line circuit (third) as repeated by the relay ZFP, causes the third stepping relay 3V to be energized from through a circuit including front contact 46 of relay SA, back contact 41 of relay ZFP, front contact 48 of relay VP, front contact 49 of relay 2V, windings of relay 3V, to As soon as the contacts of the relay 3V are picked up, a stick circuit is closed from through a circuit including front contact 45 of relay SA, front contact 5'! of relay 3V, windings of relay 3V, to

Although the stick circuit for relay VP, including back contact 55 and front contact 45, is opened when relay 3V is picked up, the other stick circuit, including front contact 5| and back contact 43, is closed prior to the response of the relay 3V.

When the relay ZFP picks up in response to the next energized condition of the control line circuit (fourth), the relay VP is deenergized as its stick circuit including front contact 5I is opened at back contact 43 of relay ZFP, and as its stick circuit including front contact 45 is opened at back contact 55 of relay 3V.

As the fourth impulse is the last in the cycle of operation for the present embodiment, the next deenergization of the control line circuit continues until the system returns to norm-a1 conditions of rest and is again initiated. When the relay SA drops its contacts a predetermined time after the beginning of such deenergized period, the stick circuits for the stepping relays are opened at front contact 45 and all of the relays assume retracted positions.

In this particular case, when an odd number of stepping relays is employed, the relay VP is already deenergized before the deenergization of the relay SA, but if it were not, as is the case when an even number of stepping relays is used, the opening of front contact 42 of relay SA would effect such a return to a normal deenergized condition.

The half step relay VP and its control circuits have been illustrated in Fig. 6 of the accompanying drawings in a simplified manner in connection with a greater number of steps in order to illustrate the extension of the circuits of such a relay for any number of steps. From this Fig. 6, it will be easily seen, in view of the above description, that the front contact 42 of relay SA governs both the pick-up and stick circuits of the relay VP insofar as the marking off of the cycles is concerned; while the contact 43 of relay 2FP selects the closure of the pick-up and stick circuits in combination with the stepping relays.

The pick-up circuits are energized only with the relay ZFP' picked up which occurs during the energized condition of the control line circuit; while the holding stick circuit for the relay VP, which holds it during the transition period between steps, is closed only with the relay 2FP deenergized. In other words, front contact 43 closes the pick-up circuits, while back contact 43 closes the holding stick circuit including front contact L In order to eliminate the useof a make-beforebreak contact for contact 13, a temporary stick circuit is associated With each pick-up circuit, that is, the closure of front contact 45 shunts out the contact 53 until after its back points areclosed for completing the holding stick circuit including front contact 5|, prior to the opening of the temporary stick circuit including front contact 45 by the response of the next stepping relay. Thus, it is to be understood that the stick contact t5 may be omitted by making contact 43 a make-beiore-break type of contact.

It is to be understood that these circuit connections may be extended for as many steps as desired with alternate stepping relays closing and opening the pick-up circuits. Such extension has been illustrated in Fig. 6 by the illustration of the relays 4V, 5V and 6V in addition tothe relays l-V, 2V and 3V shown in: Fig. 3, for example.

The stepping relay banks at each of the field stations (see Fig. 4, for example) are substantially identical in function with but few changes in arrangement. For example, the stepping bank at the field station is caused to be operated by the FP relay (see Fig. 4) instead of by its repeater, as in the control ofiice. Also, the control circuits for the stepping bank employ some of its controlling contacts in common with other circuits and the stepping operation is dependent upon the type of cycle, in a manner presently to be described.

Impulsing of control line circuit-The initial application of the first impulse to the control line circuit, accomplished as previously explained, results in the successive energization of the relays F, FP, ZFP, SA and VP. As soon as the contacts of the relay VP are picked up, an energizing circuit is completed for the impulsing relay E from through a circuit including back contacts 83 84 and 85, lower winding of the relay E, front contact 86 of relay VP, to I'nis energization of the relayE opens back contact 21 included in multiple with the contact 28 of the relay EP, but the con-rol line circuit is not opened until both of these contacts have opened. However, closure of front contact 81 of the relay E completes an energizing circuit for the repeating relay EP, so that after a time the back contact 23 is also opened.

The deenergization of the control line circuit is repeated by the relays F, FF and ZFP, but the relay SA is sufficientl'y slow acting to maintain its contacts in picked up positions until the succeedingapplication of energy to the control line circuit.

The deenergization of the relay 2FP causes the first stepping relay W tobe energized, as previously explained, and the picking up of its contact 85' opens the energizing circuit for the relay E allowing its contacts to drop away. The closure of back contact 21 completes the control line circuit and energizes it with a polarity in accordance with the position of the polar contacts of the relay D, as positioned: duringthe. preceding conditioning period, as previously explained..

Thesopenihg of contact 31' oi the relay E deenergizes the relay EP, so that back contact 28 is closed and the line circuit is again completed through contacts 2.3: and 28. irrmultiple.

The: energization of the line circuit is repeated by the relays F, FF and EFT, and as soon as the contact143 of the: relay ZFP is picked up, the relay VP is deenergized, thus completing a pick-up circuit for the relay E from through a circuit including back contacts 83 and 85 of stepping relays 3V and 2V respectively, front contact 35 of relay l V, upper winding of relay E, back contact 86 of relay VP, to This energization of the relay E is repeated by the relay EP and the control line circuit is again deenergized.

The relays F; FP, 2FP, VP, E, EP and the stepping relays continue in what may be termed cycle operations, until the last impulse has been placed upon the control line circuit, after which the control line circuit is maintained opened to cause the system to enter a period of rest, in a manner to be explained later.

In brief, the initial period of energization of the control line circuit includes the pick-up periods of the relays F, FP, 2FP', SA, VP, E and EP; while the succeeding periods of energization include the pickup periods of the relays F, FP, AFP, VP, Eand EP. Then the deenergized or conditioning periods between successive impulses applied to the line circuit include the drop away periods of the relays-F, FP and ZFP, the pickup period of a stepping relay, and the drop away period of the relay E. From this it can be seen that the relay EP is provided to prolong the energized period of the line circuit, as the circuit is not opened by the contactZl of the relay E, but by the contact 28' of the relay EP; while the closure of the line circuit is accomplished by contact '21 of relay E instead of the contact 28 of the relay EP.

Station selection for controls-The application of'a predetermined number of impulses of selected polarities to the control line circuit to comprise a cycle of operation has been explained in detail. For the transmission of controls, the first impulse of such a cycle is always positive in character, while the following impulses are positive or negativebeing arranged in accordance with the particular code jumpers and control levers which are effective for that cycle. It will be obvious by considering the line circuits of Figs. 1 and 2 that these impulses are received at all of the field stations, but for convenience in describing the operation of a field station, reference will be made to Fig. 4 which illustrates a typical field station in detail and which, for convenience, is considered to be the first station.

The application of the first positive impulse to the line circuit causes the line relay F to actuate its contacts to right hand positions. The closure of contact tit of relay F in a right hand position energizes the relay FP which in turn energizes the slow acting relay SA through a ci cuit including front contact 5 i It if of course understood, that the first impulse is somewhat longer than the remaining impulses of the cycle which is for the purpose of picking up the slow acting relays 8A (with suitable exponents) at each of the field stations.

Duringthe: pick-up periods of the relays FP and SA- at the beginning of each cycle, the quick acting two-position polar magnetic stick type cycle checking relay 0K is positioned in accordance with the polarity of the first impulse. In this case,.the first impulse ispositi've in. character' thereby closing 'a circuit for. the relay (2K from (B+), through a circuit including polar contact 62 of relay F in a right hand position, back contact 63 of relay SA windings of relay CK to (CN). This energization of the relay CK with positive potential actuates its contact to a right hand position which permits the stepby-step operation at the field station.

A cycle checln'ng relay OK (with suitable exponents) is similarly positioned at each of the field stations thereby permitting step-by-step operations to occur at every field station in the system.

On the other hand, if the first impulse were negative, for reasons later to be explained, the polar contacts of relays F (with suitable exponents) would be actuated to left hand positions thereby placing negative potential from (B) on the relays CK (with suitable exponents). This would prevent the operation of the stepping relay bands at all of the field stations except at that field station which had initiated the cycle of operation, as explained later.

For the present it is sufficient to know that the cycle checking relays OK at the field stations have registered a positive impulse and that'the stepping relay banks at the field stations are conditioned to operate through a cycle of operation in response to the impulses placed upon the control line circuit.

In due time the relay SA picks up its contacts, at which time, with the contacts of the relay FP already picked up, a circuit is completed for energizing the relay VP from through a circuit including front contact 554 of relay 3A polar contact 85 of relay K in a right hand position, front contact 66 of relay FP back contact 6'! of relay V windings of relay VP to Upon the picking up of the contacts of the relay VP its temporary stick circuit is closed from through a circuit including front contact 68 of relay SA front contact 69 of relay VP back contact 61 of relay 1V windings of relay VP to The following deenergization of the control line circuit is repeated by the relay FP thereby completing a holding stick circuit for the relay VP from through a circuit including back con tact M of the relay FP front contact '10 of relay SA front contact H of relay VP windings of relay 'v'P to This stick circuit is closed before the stick circuit including front contacts 5' and 89 is opened at back contact 67 upon the picking up of the first stepping relay IV With the relay F'P deenergized, the pick-up circuit for the first stepping relay W is closed from through a circuit including front contact 5 5 of relay SA}, polar contact 65 of relay 0K in a right hand position, back contact 65 of relay FP front contact 72 of relay V1 back contact T5 of relay 2V windings of relay 1V to As soon as the contacts of relay W assume picked up positions, a stick circuit is closed from through a circuit including front contact lid of relay 5A front contact 14 of relay 5V windings of relay IV to It is considered unnecessary to explain further step-by-step operations of the stepping relay bank at the field station, as its operations are identical with that explained for the control ofiice with the exception that its pick up circuits inch-id e the polar contact 65 of relay CK in a right hand position. It will also be noted, that the circuits for the relay VP include several additional contacts on the relays SA and FF, but these changes are merely to accommodate the cult is selected through contact arrangement rather than to change the function, as the same contact and circuit arrangement may just as well be employed at the field station.

The first stepping relay is picked up during the conditioning period of the first step, that is, during the deenergization of the control line circuit following its first energization. Thus, the polar contact 62 of the relay F is in a deenergized position upon the picking up of the contacts of the stepping relay lV In other words, the polarity of the first impulse is executed or stored in the checking relay 0K then the first stepping relay IV is energized upon the following deenergized condition of the control line circuit, so that upon the second deenergization of the control line circuit, the character of such impulse will be stored or executed in the first station selecting relay at each of the field stations.

For example, at this field station (see Fig. 4) the relay iST is energized by a circuit closed from either (B+), or (B), depending upon the character of the impulse with polar contact 62 of relay F in right or left hand positions respectively, through a circuit including front contact 63 of relay SA back contact 15 of relay 3V back contact it of relay 2V front contact 51 of relay lV windings of relay lST to (ON).

As pointed out above, the character of this second impulse is determined in accordance with the position of the code jumper 33 in the control oiiice, so that with code jumper 33 in an upper position, a positive impulse is placed upon the line circuit which causes placed upon the relay lST actuating its contacts to right hand positions; while if the code jumper 33 is in a lower position, a negative impulse is placed upon the control line circuit which causes negative potential to be placed on the relay EST actuating its contacts to left hand positions.

During the conditioning period following the second impulse on the control line circuit, the second stepping relay 2V is energized and its contacts are picked up, while the polar contact 62 of relay F is in its biased-to-neutral position.

Upon the application of the third impulse of the cycle, the character of which is determined in accordance with the position of the code jumper 34, the station selecting relay 2ST is energized with positive or negative potential in accordance with the character of such impulse. Thus, with code jumper 34 in an upper position, the third impulse is negative in character and the relay 2ST is energized by a circuit closed from (B-), through a circuit including polar contact 62 of relay F in a left-hand position, front contact 63 of relay SA back contact 15 of relay 3V front contact 16 of relay 2V windings of relay 2ST to (ON). The current which fiows in this circuit actuates the contacts of the relay ZST to left hand positions.

In brief, there are a plurality of code determining means in the control ofiice, each including a code determining relay and a set of code jumpers, only one of which may be effective to determine the character of the impulses of any particular cycle. Then during the first part of each cycle, the station selecting relays I ST and 2ST (with suitable exponents), at each field station'are positioned in accordance with the positions of the code jumperswhich are effective for that cycle of operation. At each field station, a different cir-' the station selecting reositive potential tobe Ill lays, so that each station requires the transmission of a different code, which code is determined in accordance with the position of its corresponding group of code jumpers in the control office.

With the use of only two station selecting relays .as illustrated, only four different code combinations are possible, three of which may be employed for station selection and the fourth for the phantom station code call, as more specifically pointed out hereinafter. These four different selections have been illustrated in Fig. '7 with the corresponding code symbols opposite each circuit selection and the relays IST and 2ST shown without control circuits and distinctive exponents, as they are typical of the station selecting relays at every field station.

It is suflicient for an understanding of the present invention to know that the code call for the field station illustrated in Fig. 4 requires a code call to properly position the relays IST and 2ST so that the succeeding impulses will be effective to position the control relays of that station, and for this reason, the

' code jumpers 33 and 34 in the control ofiice (see Fig. 3) are positioned to apply this code combination when the code determining relay CD is picked up.

Transmission of controls.-Assuming that the proper code combination is applied to the line circuit and that the station selecting relays IST and 2ST are properly positioned, as previously explained, then upon the application of the fourth impulse to the control line circuit, the character of which is determined in accordance with the position of the control lever SML in the control ofiice, the switch machine control relay SMR is energized either from (B+) or (B) depending upon the character of the impulse applied to the control line circuit, through a circuit including polar contact 62 of relay F in a right or a left hand position respectively, front contact 63 of relay SA front contact 75 of relay 3V polar contact '18 of relay IST in a right-hand position, polar contact 19 of relay 2ST in a left-hand position, windings of relay SMR to (CN) Thus, with lever SML in a right-hand position, a positive impulse will be placed upon the control line circuit and positive potential from (3+) will be applied to the relay SMR. actuating its polar contact to a right-hand position, thereby applying energy to the normal operating wire 8| of the switch machine SM which operates the track switch TS to its normal locked position; while, if the lever SML is in a left-hand position, a negative impulse will be placed upon the control line circuit and negative potential from (B) will be applied to the relay SMR actuating its polar contact 86 to a left-hand position thereby applying energy to the reverse operating wire 82 of the switch machine SM which operates the track switch TS to a reverse locked position.

In a similar manner, any number of additional steps may be provided for transmitting additional controls to this field station, for governing the signals and such other devices as may be necessary.

End of operating cycle.Upon the application of the fourth impulse to the control line circuit (the last impulse of the cycle), the half step relay VP in the control office (see Fig. 3) is deenergized. This completes a pick-up circuit for the impulsing relay E from through a circuit including front contact 83 of relay 3V, upper wind? ris, f relay Em cs c nta t {150i r lay VP, o

The energization of the relay E is repeated by the relay EP and the control line circuit is deenergized, but the resulting deenergization of the relay ZFP is not effective in this case, to energize another stepping relay, as the relay 3V is the last. Thus, the energizing circuit for the relay E is maintained closed thereby continuing the deenergized condition of the control line circuit beyond the normal period of time between the succeeding impulses of a cycle of operation.

The continued deenergization is suificiently long for the relays SA (with suitable exponents) at the control ofiice and at the field stations to allow their contacts to drop away. Upon the opening of the front contacts the relays SA (with suitable exponents) at the several locations, the stick circuits of all the stepping relays IV, 2V and 3V, (with suitable exponents) at those locations are opened and their contacts drop away. In the control office this deenergizes the relay E and in turn deenergizes the relay EP.

Simultaneously with this dropping away of the stepping relays, the opening of the front contact 2| of relay SA in the control office with the back contact l9 of relay ZSA still open, the cycle controlling relay C is deenergized thereby opening the selective control circuit of the relay D so that its contacts assume deenergized positions. Thus, upon the closure of the back contacts 21 and 28 in the line circuit, the contacts of the relay D have assumed biased-to-neutral positions and the control line circuit continues to be deenergized. Such continued deenergization causes the system to enter a condition of rest or a period of blank.

Also, that particular code determining relay effective for the last cycle of operation is deenergized at the end of the last impulse applied to the line circuit, so that the next code determining relay in order may be effective at the beginning of the next cycle of operation assuming of course that its corresponding starting button has been actuated.

However, it is to be noted, that the actuation of another starting button (or a stored actuation of a starting button) cannot be effective to energize the starting and cycle control relay 0 until the slow acting relay 2SA has assumed its deenergized position by reason of back contact l8. Also, the field stations cannot be effective to start a cycle of operation until the relay ZSA has become deenergized by reason of back contact 9B. In other words, the relay vZSA, besides furnishing a convenient means in combination with the relay SA for closing and opening the stick circuits of the relays C and FC, also provides means which prolongs the deenergized restoring period at the end of a cycle of operation for an additional time to allow sufficient margin for all of the field stations to return to their normal at rest conditions.

Transmission of indicati0ns.-The selection of field stations for outgoing controls and the transmission of these controls is all accomplished, as above explained, over the control line circuit; while the message or indication line circuit is employed in accordance with this invention for the transmission of indications to the control office after the registration of that particular station which has the new indications to transmit.

Although this system is of the coded duplex type, and indications may be transmitted from any station to the control office simultaneously and during the same operating cycle that con.-

trols are transmitted to the same or some other station, it is convenient to first explain the communication of indications alone on a separate operating cycle before considering the duplex feature of the system.

There may be trains on various portions of the territory under the supervision of the operator, and these trains may enter or leave track cirsuite at two or more points in the territory at substantially the same time, and likewise the switches and signals at the various locations may be operated in such a way from time to time by the operator that several of these trafiic controlling devices may assume new conditions at substantially the same time. Thus, it will be evident that when two or more field stations have new indications to communicate to the control ofiice at the same time, some means must be provided to allow only one of these field stations to transmit at any one time to avoid mutilation of the registration of the code calls and to avoid the transmission of erroneous or false indications.

The way in which the field stations are allowed to transmit only one at a time in a predetermined order or sequence is more conveniently explained following a description of the operation of the system with respect to the transmission of indications from a single field station, assuming that such station is the only one having new indications to transmit at the beginning of the operating cycle.

Automatic starting from a field station.-With reference to Fig. l of the accompanying drawings, a change in the condition of the detector track section may occur at any time and similarly the change in condition of other traffic controlling devices at the station may also occur at any time, but for the purpose of disclosing the present invention, only a change in the track relay T has been illustrated as eifecting the change relay CH However, it is to be understood that the changes of other devices will similarly momentarily open the stick circuit of the change relay CH For example, the movement of the contact l5 of the track relay T from a front point to a back point, or vice versa, momentarily opens the stick circuit of the relay CH for a sufficient time to allow its contacts to assume deenergized positions. The deenergization of the relay CH completes a pick-up circuit for the relay CHS when the system is at rest or in a period of blank, from through a circuit including back contact iii of relay FP back contact iii of relay SA lower winding of the relay CHS back contact I E15 of the relay CH to The closure of front contact 1B! of the relay CHSPconnects the indication line wire l4 through a circuit in' cluding back contact 1102 of the relay SA upper winding of the relay L0 compensating resistance R to the common return line wire l2.

As the system is in a period of rest or blank, the relay EFP at the control oflice is deenergized, so that a circuit is completed for the energization of the relay MEB and the relay LO at this field station in series. More specifically, this starting circuit is closed from the positive terminal of the indication battery 13, through a circuit including the lower winding of the relay MEB, back contact I03 of the relay ZFP, indication line it to the first station, front contact llll of relay Cit-IS at that station, as it is the one that is initiating the system, back contact H32 of the relay SA upper winding of relay,LO ,.re-

sistance R to the common return line [2, thence to the control ofiice to the negative terminal of the indication battery IB.

Energization of the lock-out relay L0 at the field station causes its contacts to be picked up, thereby closing a stick circuit for the relay CI-IS from through a circuit including back contact 54 of relay SA front contact I04 of relay L0 front contact H35 of relay CHS lower Wind- I ing of relay CHS back contact Hill of relay CH to The fact that new indications are ready to be transmitted is now registered both in the control office and at the first field station.

In the control oifice, the picking up of the contacts of the relay LEE closes a pick-up circuit for the field starting and cycle controlling relay F0 from through a circuit including front contact 89 of relay MEB, back contact 90 of relay ZSA, upper winding of relay FC, to

t has been assumed for convenience that only a change at a single field station has occurred and that there are no controls to be transmitted. Thus, the control oifice starting and cycle controlling relay C is deenergized which allows the field starting and cycle controlling relay FC to connect negative potential directly to the polarity determining relay D from (B), through a circuit including front contact I96 of relay FC, back contact 25 of relay C, windings of relay D, to (ON) This energization of the relay D causes its contacts to be actuated to left hand positions, thereby applying negative potential to the control line circuit, which energization is repeated at the control office and at each of the field stations by the line relays F (with suitable exponents).

At the control office, the energization of the line relay F is repeated by the relays FP, ZFP, SA and 23A in succession. Similarly at the first field station, for example, the energization of the relay F is repeated by the relays PP and SA in succession.

The picking up of the contacts of the relay FP at the field station marks: the end of the initiating period (during which any other field station may pick up its change storing relay CHS, as explained hereinafter) by reason of the opening of back contact 6| which is included in the pick-up circuit of the relay CI-IS However, the change storing relay CHS and its associated lockout relay L0 are not positively locked up for a cycle of operation through their stick circuits until the relay SA has responded. But during the time the relay SA is responding, the relay 01-18 is held up through back contact 64 of relay SA and a front contact l 94 of relay L0 while the relay L0 is held up by energy received over the indication line circuit as previously pointed out.

This continued energization of the relay L0 is maintained although the relay ZFP in the control office picks up prior to the picking up of the relay SA at the field station, because the contact 103 of this relay 2FP is a make-before-break contact and merely routes the indication line circuit through the winding of the relay MEF and front contact I03 instead of through the lower winding of the relay MEB and back contact I03.

Then upon the picking up of the relay SA at the field station, the look-out relay L0 and the change storing relay CHS are energized in series by a circuit closed from through a circuit including front contact 64 of relay SA front contact I01 of relay L0 lower winding of relay L upper winding of relay CI-IS front contact m8 of relay CHS to As the contact 64 of relay SA is of the makebefore-break type, this stick circuit is completed prior to the opening of the stick circuit for the relay CHS through back contact 64 of relay SA front contact iilfi of relay L0 and front contact Hill of relay CHS It is also noted that the contact Hi2 of relay SA is a break-beyond-- center contact (not a make-before-break), so that the indication line circuit includes the relay L0 up to the time that its stick circuit, including front contact E i, is closed.

In the control office, the picking up of the contacts of the relay SA completes a stick circuit for the field starting and cycle controlling relay PC from through a circuit including front contact Hi9 of relay SA, front contact Ill) of relay FC, lower winding of relay FC, to Also, the closure of front contact 42 of relay SA permits the energization of the half step relay VP, as previously pointed out, which in turn causes the energization of the impulsing relay E. Upon the repeating of the relay E by the relay EP, the control line is opened and the stepby-step operatic-n of the system through a cycle is insured and continues in a manner similar to that explained in connection with the transmission of controls.

However, it is to be noted, that the first impulse placed upon the control line circuit is negative in character by reason of the energized condition of the relay FC and the deenergized condition of the relay C. These relays are maintained in such conditions throughout the cycle of operation, because the pick-up circuit of the relay 0 is maintained open at back contact E8 of relay ZSA. Thus, the relay D continues to be energized with negative potential throughout the cycle, which results in the application of a negative impulse upon the control line circuit for each impulse of the complete cycle of operation.

Although the relay FP and the relay E have their contacts in raised positions at the same time during the latter part of the first impulse placed upon the control line circuit, the conditions of the relays MEB and MEF are not executed, as the first stepping relay iV is still de energized and its front contacts are open. Similarly, at the field station, although the control of the indication line is made dependent upon the position of the relay PL as soon as the front contact H32 of the relay 8A is closed, the indication line is not conditioned in accordance with an indication contact until the first conditioning period, that is, the deenergized condition of the control line circuit following the application of the first impulse at which time the first step-ping relay IV is picked up.

Registration of a field station.At the field stations the character of the first impulse of the cycle is stored in the cycle checking relays CK (with suitable exponents), as previously explained. But in this case, where the cycle of operation is for the transmission of indications alone, the first impulse is negative, as Well as all succeeding impulses, so that the polar contacts of the relays CK (with suitable exponents), are actuated to left hand positions. This prevents the stepping relay banks from operating at the several stations insofar as the relays CK are con cerned.

However, at that particular station having indications to transmit, the look-out relay LO (with suitable exponent) is energized, so that upon the picking up of the relay SA (with suitable exponent) during the application of the rst impulse to the control line circuit, the relay VP (with suitable exponent) is energized at this particular station as before, the only difference being that its pick-up circuit includes a front contact of the relay L0 (with suitable exponent) instead of a polar contact of the relay CK (with suitable exponent).

For example, the pick-up circuit of the relay VP is closed from through a circuit including front contact 64 of relay SA front contact III of relay L0 front contact 66 of relay FP back contact 61 of relay IV windings of the relay VP to The further control of the relay VP is similar to that previously pointed out and need not be explained in detail.

Similarly, as the control of the relay VP is now dependent upon the front contact H! of the relay L0 likewise the pick-up circuits of the stepping relays also include the front contact III of relay LO instead of the polar contact 65 of the relay 0K in a right hand position. In other words, the first field station, where contact H I of the relay L0 is closed, is the only station in this case where step-by-step operations can take place.

Thus, upon the deenergization of the control line circuit following the application of the first impulse, the first stepping relay [V is energized by a circuit from through a circuit including front contact 54 of relay 8A front contact I H of relay L0 back contact 66 of relay FP front contact '52 of relay VP back contact of "E3 of relay 2V windings of relay lV to The further control of the stepping relays [V 2V and 3V is similar to that already pointed out and need not be explained in detail.

As soon as the contacts of the relay IV assume picked up positions, the relay PL is immediately conditioned in accordance with the particular indication contact for that conditioning period. In this case, the code assigned to this station for registering itself in the control office is Thus, the code jumper H5 is placed in a lower contacting position for completing an energizing circuit for the relay PL from through a circuit including code jumper H5, front contact IE of relay IV back contacts H1 and H8 of relays 2V and 3V respectively, back contact H9 of relay FP windings of relay PL to This energization of the relay PL causes the indication line circuit to be completed, but as the control line is deenergized, the relay MEB is the particular message relay included therein.

More specifically, the indication line circuit is closed from the positive terminal of battery IB, through a circuit including the lower winding of relay MEB, back contact 553 of relay ZFP, indication line H, front contact Ill! of relay CHS front contact I02 of relay SA front contact I20 of relay PL resistance R common return line l2, to the indication battery IB. This circuit energizes the relay MEB which is continued during the following execution period by reason of a stick circuit from through a circuit in cluding front contact 89 of relay MEB, front contact l2! of relay FP, upper winding of relay MEB, to

On the other hand, if the code jumper I I5 is in an upper non-contacting position, the relay PL remains deenergized which in turn allows the message relay MEB to remain deenergized for the conditioning period of this step and the executing period of the next.

In other words, the relay'MEB is positioned during a conditioning period, which position is maintained through the following executing period, so that the indication thus transmitted to the control ofiice can be properly stored or executed during such executing period.

The application of the next impulse to the control line circuit is repeated by the relay 2F? at the control ofiice and the relay FP at the field station which causes the indication line to include the relay MEF, and the control of the relay PL to include a front contact of the relay FP For example, the relay PL is energized or left deenergized depending upon whether the code Jumper I22 is in a contacting or a non-contacting position. The code call chosen for this station has been assumed to be thus, the code jumper I22 is left in a non-contacting position and the relay PL remains deenergized to transmit a impulse. On the other hand, if some other code call is used requiring a code impulse, then the code jumper I22 is moved to a contacting position in which an energizing circuit is closed from through a circuit including code jumper I22 in a contacting position, from contact I23 of relay IV back contacts I24 and I25 of relays 2V and 3V respectively, front contact I I9 of relay FP windings of relay PL to Depending .upon whether the relay PL is energized or deenergized, the indication line circuit is energized or deenergized, respectively. As the front contact I83 of relay 2FP is closed the indication line circuit includes the message relay MEF, so that the condition of the indication line circuit is repeated by this relay.

In other words, during the conditioning. period of a step, the pulsing relay PL (with suitable exponent) at a station is conditioned through a back contact of the relay FP (with suitable exponent) in accordance with the opened or closed position of a code jumper; and similarly, during the executing period of the next step, the relay PL (with suitable exponent) is conditioned through a front contact of the relay FP (with suitable exponent) in accordance with the condition of another code jumper. In both cases these conditioning circuits for the relay PL include the front contacts of the same stepping relay.

In the control oifice, the conditioning of the relay MEB through back contact I03 of the relay ZFP during the conditioning of a step is maintained during the following executing period (of cluding the front contact I2! of relay FT; while the relay MEF assumes its condition during such following executing period. These conditions set up in the relays MEB and MEF during the respective periods in accordance with the condition of the relay PL (with suitable exponent) on such periods, are executed or stored near the end of such executing period during the time that the relay E is picked up before the relay FP drops in response to the opening of the line by the relay EP. This storing period of time for indications includes the pick-up period of the relay EP and the drop away periods of the relays F and FF.

For example, in the particular case assumed.

Where the code call transmitted is the relay MEB is picked up and the relay MEF is deenergized at the time that the relay E is picked up near the end of the executing period of the first step, so that the pilot relays IPB and IPF are energized with positive and negative potentials respectively.

More specifically, the relay IPB is energized with positive potential from (B+), through a circuit including front contact I26 of relay MEB, front contact I21 of relayFP, front contact I28 of relay E, back contact I29 of relay 3V, back contact I30 of relay 2V, front contact I3I of relay IV, windings of relay IPB, to (ON). This application of positive potential to the relay IPB causes its polar contacts to be actuated to right hand positions.

Similarly, the relay I PF. is energized with negative potential from (B) including back contact I32 of relay MEF, front contact I33 of relay FP, front contact I34 of relay E, back contact I35 of relay 3V, back contact I36 of relay 2V, front con;- tact I31 of relay IV, windings of relay IPF', to (CN). This application of negative potential to the relay IPF causes its contacts to be actuated to left hand positions.

It is of course obvious that if some other code combination were transmitted, the relays MEB and MEF would be positioned in accordance therewith and their corresponding pilot relays would be energized with polarities determined thereby.

In any event, the station registering pilot relays IPB and IPF, being positioned as described, have selections made through their contacts in a similar manner as if they were controlled on individual steps rather than upon the same step. In other words, selections are made through their contacts for the control of the indication storing relays IR- of the several field stations (only one being shown) in a similar manner, as explained for the relay SMR associated with the station selecting relays I ST and 2ST with reference to Figs. 4 and '7.

Also, it should be understood that pilot relays may be positioned on any desired number of steps, but for the sake of simplicity only one step has been employed for this purpose in the illustration of the present embodiment.

However, for the purpose of illustrating the large number of code combinations obtained for each added step, a code table for a system having two steps is shown in: Fig. 8. The symbols and indicate the right and left hand positions respectively of the contacts of the relays IPB and IPF, also the relays 2PB and ZPF (relays not shown in Fig. 3).

From this code table, it can be seen that on. two steps, sixteen different code combinations or selections through the station registering pilot re lays may be made. It should be understood in this connection, that the sixteenth or last combination composed of all symbols causes the continued deenergization of the indication line throughout a cycle of operation for the transmission of controls alone, which results in the failure of the system to register any station.

It may be noted here, that the use of relays PP and 2FP facilitate the sticking up of the relay MEB. In other words, the relay FP always closes front contact I2I before back contact I03 of relay 2FP is opened, by reason of the sequential operations of these relays.

Transmission of indications.-After thus having registered in the control ofiice the particular field station which has its indications ready to transmit, the remaining steps of the cycle are employed for the transmission of indications.

For example, on the deenergized condition of the control line circuit, following the application of the second impulse, the second stepping relays 2V (with suitable exponents) are picked up. As

.the relays ZFP and FP .are deenergized, the relay MEB is .included in theindication line'circuit and the. relay PL is controlled in accordance with the contact I40 of the track relay T. If the track relay T is energized, the relay PL will remain deenergized; but if the track relay T is deenergized, the relay PL will be energized by a circuit closed from through a circuit including back contact I40 of the relay T, iront contact I ll of the relay 2V back contact I I8 of the relay 3V back contact I I9 of the. relay FP windings of the relay PL to With the relay PL deenergized, the indication line circuit is deenergized and the relay MEB is positioned accordingly; while, with the relay PL energized, the indication line circuit is energized and the relay MEB is picked up, as previously explained.

Then upon the application of the next impulse (third), the relay MEB is maintained in its condition set up on the preceding conditioning period, that is, if it is deenergized it remains in such condition, but if energized it remains energized by reason of its stick circuit. Also, during this executing period, the relay MEF is positioned in accordance .with the condition of the relay PL as controlled through front contact Ill") of relay FP and front contact I24 of the relay 2V by a suitable indication contact.

Although there is no controlling indication contact illustrated for the relay PL for this period, it is to be understood that such control is provided in a similar manner as illustrated for the front contact II! of the relay 2V by the relay T.

Such control would position the relay MEF, and upon the picking up of the relay E near the end of the third impulse, the positions of the relays MEB and MEF are executed or stored in the proper indication storing relays for the second step.

For example, the relay IR, is energized with positive or negative potential depending upon whether the relay MEB is energized or deenergized respectively, by a circuit either from (13+) or (B-), through a circuit including front or back contact I26 of relay MEB, front contact I21 of relay FP, front contact I28 of relay E, back contact I29 of relay 3V, front contact I30 of relay 2V, polar contact I4! of relay IPB in a right hand position, polar contact I42 of relay IPF in a left hand position, windings of relay IR, to (CN).

The actuation of polar contact I43 of relay IR to a right hand position in response to the application of positive potential to relay IR where back contact I40 of relay T is closed, completes a circuit for the track occupancy indicating lamp OS, as will be obvious from the drawings. This indicates to the operator the presence of a train on the corresponding detector track section.

Although only the transmission of indications on a single step has been explained in detail, it is to be understood that any number of steps may be similarly employed, each such step providing for the transmission of two additional indications.

During a cycle of operation for the transmission of indications, as just explained, the change relay CH (with suitable exponent) at the field station, which just transmitted, is restored to a picked up position in readiness for any other changes that may occur at that field station.

For example, the relay CH is picked up during the time that the relay IV is picked up before the relay 2V is picked up. More specifically, this pick-up circuit is closed from through a circuit including front contact'I44 of relay L0 front contact I45 of relay IV back contact I46 of relay 2V windings of relay CH to As this pick-up circuit is closed but a short period of time, the'relay CH is always in readiness to receive a change in conditions and store that change.

End of indication cycle-The step-by-step operation of the system and the impulsing of the control line circuit during an indication cycle is similar to those operations during a control cycle, and the control line circuit is opened at the end of the last impulse in a similar manner, as previously explained, which allows the relays of the system to assume normal positions. The drop away of the relay SA in the control office opens the stick circuit of the relay PC, so that the control line remains deenergized until the system is again initiated.

Inasmuch as the change relay CH at the field station has been restored, the dropping away of the relay SA opens the stick circuits for the relays L0 and CH8 in series including front contact 64 of relay SA front contact IEl'I of relay L0 lower winding of relay L0 upper winding of relay OHS, and front contact I08 or relay CHS and these relays then drop away. Even if the indication line circuit could be closed momentarily through front point IIII of relay CI-IS and back contact I02 of relay SA this momentary energization would prove ineifective to initiate another indication cycle of operation, inasmuch as the energization of the relay MEB cannot be effective to pick up the relay FC until the relay ZSA is deenergized. This relay 25A is sufiiciently slow acting to allow all of the relays oi the system to assume their normal positions after the dropping of the contacts of the relays SA (with suitable exponents) before its contacts assume their retracted positions.

Lock-out between field stations for transmission of indications.-As previously mentioned, it may happen that changes may occur at several of the field stations at the same time or in rapid succession, so that more than one field station will have new indications to transmit at the beginning of an operating cycle. In order to prevent more than one field station from actually transmitting indications during any particular cycle of operation, lock-out means is provided at each field station which is effective to select that field station nearest the control ofiice which has new indications to transmit at the beginning of an operating cycle.

The system has what may be termed an initiating period and a lock-out period at the beginning of each cycle of operation. The initiating period may be said to include the time which elapses between the occurrence of a change condition either in the control office or at a field station up to the instant that the quick acting line repeating relays F? (with suitable exponents) at the control ofiice and at each field station pick up their contacts in response to the first impulse applied to the control line circuit; while the look-out period may be considered as that time which elapses between the actual picking up of the contacts of the relays FF and the picking up of their respective slow acting relays SA.

The various operations or functions of the system during the initiating period and the lock-out period may be best understood by considering the line circuits illustrated in Figs. 1 and 2 of the accompanying drawings.

Whenever a change occurs at a field station, as 

